Drug-resistant and hospital-associated Enterococcus faecium from wastewater, riverine estuary and anthropogenically impacted marine catchment basin

Aneta Luczkiewicz,Ewa Sadowy

doi:10.1186/1471-2180-14-66

Aneta Luczkiewicz, Ewa Sadowy

Open Access

https://doi.org/10.1186/1471-2180-14-66

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Abstract

BackgroundEnterococci, ubiquitous colonizers of humans and other animals, play an increasingly important role in health-care associated infections (HAIs). It is believed that the recent evolution of two clinically relevant species, Enterococcus faecalis and Enterococcus faecium occurred in a big part in a hospital environment, leading to formation of high-risk enterococcal clonal complexes (HiRECCs), which combine multidrug resistance with increased pathogenicity and epidemicity. The aim of this study was to establish the species composition in wastewater, its marine recipient as well as a river estuary and to investigate the antimicrobial susceptibility of collected isolates. Molecular methods were additionally applied to test the presence of HiRRECC-related E. faecium.ResultsTwo wastewater treatment plants (WWTPs), their marine outfalls and Vistula river that influence significantly the quality of waters in Gulf of Gdansk were sampled to investigate the presence of Enterococcus spp. Four-hundred-twenty-eight isolates were obtained, including E. faecium (244 isolates, 57.0%), E. hirae (113 isolates, 26.4%) and E. faecalis (63 isolates, 14.7%); other species (E. gallinarum/casseliflavus, E. durans and E. avium) accounted for 1.9%. Antimicrobial susceptibility testing revealed the presence of isolates resistant to erythromycin, tetracycline, amipicillin, fluoroquinolones and aminoglycosides (high-level resistance), especially among E. faecium, where such isolates were usually characterized by multilocus sequence types associated with nosocomial lineages 17, 18 and 78 of this species representing HiRECC, formerly called CC17. These isolates not only carried several resistance determinants but were also enriched in genes encoding pathogenicity factors (Esp, pili) and genes associated with mobile genetic elements (MGE), a feature also typical for nosocomial HiRECC.ConclusionsOur data show that WWTPs constitute an important source of enterococcal strains carrying antimicrobial resistance determinants, often associated with the presence of MGE, for the recipient water environment, thus increasing a pool of such genes for other organisms. The presence of HiRECCs in wastewaters and marine/river environment may indicate that adaptations gained in hospitals may be also beneficial for survival of such clones in other settings. There is an obvious need to monitor the release and spread of such strains in order to elucidate better ways to curb their dissemination.

Highlights

Enterococci, ubiquitous colonizers of humans and other animals, play an increasingly important role in health-care associated infections (HAIs)
Species composition and antimicrobial susceptibility of enterococcal isolates In this study, the number of enterococci in wastewater treatment plant (WWTP) effluents (W-EFF and Debogorze effluent (D-EFF)) remained high for both WWTP, yielding up to 6.1x105 CFU per 100 mL (Table 1), the WWTP Gdansk-Wschod showed over 99% efficiency in the removal of enterococci
428 isolates were collected, including 243 isolates from wastewater, 116 isolates from marine outfalls, and 69 from Vistula River mouth (Table 1). These 428 isolates were mainly identified as E. faecium, Enterococcus hirae (113 isolates, 26.4%) and E. faecalis (63 isolates, 14.7%), with an occasional occurrence of E. gallinarum/ casseliflavus, E. durans and E. avium (4, 3, and 1 isolates, Table 1 Presence (CFU 100 mL−1) of enterococci, number (%) of enterococcal isolates recovered and species composition at particular sites

Summary

Introduction

Enterococci, ubiquitous colonizers of humans and other animals, play an increasingly important role in health-care associated infections (HAIs). Resistance to ampicillin, associated with the changes in penicillin binding protein 5 (PBP5) and resistance to quinolones, determined by point mutations in genes encoding bacterial gyrase and topoisomerase IV are characteristic phenotypic features of nosocomial E. faecium [11,12]. Such strains commonly carry resistance genes to other classes of antimicrobials, such as tetracyclines {tet(M), tet(L), tet(S) and tet(O)}, macrolides {erm (B)} and aminoglycosides [13]. Hospital-associated E. faecium is enriched in several virulence factors, such as enterococcal surface protein (Esp) and MSCRAMM proteins [14,15,16]

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